This invention relates to finely divided particulate inorganic antimony compounds, and more particularly, to antimony oxides and sulfides which are surface modified with up to about 5% by weight of an organo silane compound.
A number of antimony compounds have been used as flame-retardants for various organic resins and elastomers. One commonly used compound is antimony trioxide. One of the difficulties associated with the use of antimony compounds such as antimony oxides and antimony sulfides to improve the flame-retardant properties of flammable organic resins and elastomers is the degradation of some of the other desirable properties of the treated elastomers and resins. Although the incorporation of small amounts of antimony oxides and antimony sulfides in conjunction with organic flame-retardant compounds into flammable resins and elastomers has improved the flame-retardant properties of the resulting product, the incorporation of such antimony compounds often has an adverse effect on other properties of the resins and elastomers such as flexural strength, impact strength, tensile strength, flexural modulus and hardness.
The above-described adverse effects are not limited to the antimony oxides and sulfides. The literature describes procedures for filling thermoplastic and other polymers with many inorganic oxides, primarily as fillers. Examples of inorganic oxides which have been used as fillers for resins and elastomers include aluminum oxide, zinc oxide, iron oxide, magnesium oxide, titanium dioxide, silicates such as kaolin clay, mica, calcium silicate and aluminum silicate, calcium carbonate such as limestone, etc. In the initial development of this art, the inorganic oxide materials, in particulate form were introduced and blended into resins and elastomers. The resulting mixtures were molded by conventional methods such as casting, injection molding, extrusion or rotational molding to form inorganic oxide reinforced plastic articles. However, it generally was found that the properties of such filled articles were not as good as expected or desired.
Various suggestions have been made in the literature for improving the results obtained when such inorganic oxide materials are incorporated into resins and elastomers. A number of suggestions for overcoming these problems have involved the use of silicon-containing compounds, and particularly silane coupling agents.
U.S. Pat. No. 3,793,288, suggests that the bonding relationship between polymers and the inorganic oxides may be improved by treating the polymer itself, rather than by treatment of the inorganic oxide. Accordingly, U.S. Pat. No. 3,793,288 applies a surface on thermoplastic polymers which comprises an organofunctional silane coupling agent and a copolymer of ethylene and acrylic acid and/or methacrylic acid. It is reported that such coated polymers, when blended and molded in combination with particulate inorganic oxides yield significant improvements in processing and in properties.
Surface modification of powdered antimony oxide with silanes is described in an article published in Applied Spectroscopy, 29 (6), pages 512-7 (1975). The authors of this article describes the surface modification of antimony oxide with chlorosilanes or by dissolving antimony oxide in hydrochloric acid prior to a reaction with an aminosilane. The incorporation of these treated antimony oxides in epoxy resins or other organic formulations in amounts ranging from 10 to 100% by weight of the modified oxide is described.
U.S. Pat. No. 3,641,087 described the use of brominated silane derivatives in combination with metal oxides such as antimony oxides and organic antimonates as flame-retardant additives for synthetic polymer compositions. The separate addition of metal oxides such as antimony oxide and other additives such as silanes and diallyl chlorendates to diallylic phthalate resins is described in U.S. Pat. No. 3,483,158. Such compositions are reported to be flame-retardant.
Considerable effort has been devoted to improving the flame-retardant properties of resins and elastomers in recent years, and the above discussed prior art merely is exemplary of these efforts.